Lord Rennard now faces investigation for bringing the Liberal Democrats into disrepute by failing to apologise to the women who made complaints against him, the party said in a statement.

The announcement has seen off a potential challenge to leader Nick Clegg's authority by preventing the former Lib Dem chief executive taking up his seat alongside the party's other peers in the House of Lords, as he had planned.

In a statement released just minutes before Lord Rennard had been expected to re-enter the Upper House, the Liberal Democrats said: "Nick Clegg made clear last week, and again this morning, that it would be inappropriate for Lord Rennard to resume the Liberal Democrat whip unless he apologises. Lord Rennard has refused to do so.

"The regional parties committee, which oversees disciplinary procedures under the English party membership rules, today decided to suspend Lord Rennard's membership of the party pending a disciplinary procedure. As such, he cannot return to the Liberal Democrat group in the House of Lords.

"Lord Rennard will now be investigated for bringing the party into disrepute on the grounds of his failure to apologise, as recommended by Alistair Webster QC."

Labour deputy leader Harriet Harman said the whole issue had been mishandled by the Lib Dem leadership.

"Nick Clegg has made an absolute pig's ear of this whole thing," she told Sky News.

"What he's done is said that the party rules are such that unless somebody has committed a criminal offence, there's nothing that can be done about it. Now they are moving on to this second issue about bringing the party into disrepute. So I think it's been a terrible muddle.

"My sympathy is with those women who have complained and are left hanging."

In a lengthy statement setting out his side of the case, Lord Rennard repeated his firm denial of having done anything intended to distress the four women who made complaints against him.

He said that he "regrets" any hurt, embarrassment or upset they may have felt, but said he would not apologise, as this would leave him "defenceless in a future civil action".

Lord Rennard said that the Lib Dems' chief whip in the House of Lords, Lord Newby, had confirmed last week that the whip was being restored and he urged Nick Clegg and other leading Lib Dems to now "let the matter rest".

"Courtesy has always been an essential part of my moral compass," said Lord Rennard.

"If ever I have hurt, embarrassed or upset anyone, then it would never have been my intention and, of course, I regret that they may have felt any hurt, embarrassment or upset.

"But for the reasons given, I will not offer an apology to the four women complainants. I do not believe that people should be forced to say what they know they should not say, or do not mean."

Lord Rennard said that he was told last Wednesday by independent investigator Alistair Webster that the conclusion of his inquiry into the women's complaints was that there should be "no further action". But he said that the party had acted contrary to its own rules by refusing to give him a copy of the report.

After learning from Mr Webster that the announcement of the report's conclusion would be accompanied by a statement saying that the women's evidence was credible and he should consider apologising, Lord Rennard contacted Lord Newby to warn him that this would cause "a major problem".

He said that he met Lord Newby and told him that he was resuming the Lib Dem whip, having voluntarily stepped aside during the inquiries, and the chief whip confirmed that he was readmitted.

"I have not spoken to, met with, or heard from Nick Clegg in 11 months," said Lord Rennard. "I would ask him, now that he has more knowledge of the facts, to ask for any threat to me to be withdrawn and to insist that I see the report, to which I am entitled, and to let me help him and my party again in future.

"I very much regret the wounds that have opened up within my party because many people have acted without being aware of the facts. I am particularly grateful to my friends and colleagues in the Liberal Democrat group in the House of Lords for much personal support.

"I would advise my friends in the party to let the matter rest, as it should have done, with the simple conclusion of the independent investigator that there should be no further action."